Pulse multiplex system



Oct. 7, `1947. G, WI GILMAN' PULSE MULTIPLEX SYSTEM Filled 'Feb.f8, 1945 s sheets-sheet 1` A TTORNE Y Oct. 7, 1947.

G. -W. GILMAN PULSE MULTlPLEX SYSTEM Filed Feb. 8, 1945 3 Sheets-Sheet 2 ATTORNEY Oct, 7, 1947.

G. W. GILMAN PULSE MULTIPLEX SYSTEM Filed Feb. 8, 1945 3v Sheets-Sheet 5 E l/vl/ENTOR Z am G/LMA/v FIT \N" WN" NN" "N" n." N",

MN" N" "N" y @am Arron/ver Patente'd Oct. 7, 1947 PULSE MULTIPLEX SYSTEM George W. Gilman, Short Hills, N. J., assigner to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application February 8, 1945, Serial No. 576,834

10 claims. (o1. `17e- 15)l This invention relates to multiplex transmission and particularly to time division multiplex in communication systems. Objects of the invention are the provision of a multiplex transmission system of the time division type in which synchronization of the sending and receiving ends is attained without reducing the number of channels available for communication and in which `channel commutationis eifected by improved and simplified apparatus and circuit arrangements.

i The invention is an improved multiplex transmission system of the time division type in which co-mmutation is effected electrically by the cyclic application of carrier impulses to the modulator of each of a plurality of voice channels in succession.

A feature of the invention is a time division multiplex transmission system in which marking impulses of one frequency are transmitted directly to a common transmission medium and carrier current impulses are transmitted through delay networksin succession to each of the modulators of a plurality of voice frequency channels, whereby the transmission of each marking impulsel over said common medium is followed hy the successive transmission of the corresponding .voice modulated carrier impulses from the modulators.

Another feature of the invention is a multiplex system of the time division type wherein timing or marking impulses incoming over a transmission medium are each applied through a chain of delay networks successively to each of a plurality of amplifiers,thereby to render the amplifiers effective to transmit each signal impulse following amarking impulse through the associated detector to a different voice channel.

' vA further feature of the invention is an arrangement of modulators common to a transmission medium in a time division multiplex system invwhich carrier impulses are transmitted successively through delay networks, the Output f each network being connected to the carrier input conductors of a plurality of modulators one in each of a plurality of groups, whereby the modulators in veach group are successively rendered effective to transmit a voice modulated carrier impulse to the transmission medium, group delay means being provided to delay the succession of voice modulated impulses from the modulators of the various groups so that the signal impulses of all `modulators are successively applied one at a time to the transmission medium following each marking impulse applied thereto.

A further feature of the invention is a receiving arrangement in a multiplex system of the time division type in which incoming marker impulses eiect the generation of switching impulses which are transmitted through delay networks in succession to each of the amplifier detectors of a plurality of voice frequency channels, whereby each of the incoming voicey modulated carrier impulses following each marker impulse is transmitted to a different vvoice frequency channel.

Another feature of the inventionis a receiving arrangement in a multiplex system of the time division type in which the'voice frequency channels and associated amplifier detectors are divided into groups corresponding f to groups of modulators in the transmitting office, means being provided to delay the transmission of the voice modulated carrier impulses-'following each marker impulse to each groupof amplifier detectors so that these impulses areapplied to each group in succession, the marker impulses being eiective to generate switching impulses which are transmitted through delay networks in succession to each of the amplifier detectors of the first group and at the same timeto the corresponding amplifier detectors of the other groups, whereby each of the incoming voice modulated carrier impulses following each marker impulse is transmitted to a different voice frequency channel. y

A clear and complete understanding of the invention will be facilitated by consideration of the system shown schematically in the drawing which forms a part of this speciiication, this system constituting a specific embodiment of the invention and its features. :The invention is, however, not limited in its application to the system shown in the drawing butwis generally applicable to multiplex transmission systems of the time division type. I

Referring to the drawing:

Fig. l shows in a first telephone -oflice a transmitting arrangement for "a multiplex communication system of the time division type;

Fig. 2 shows in a second telephone office a receiving arrangement for a time division multiplex communication system having a transmitting arrangement according to Fig; 1;

Fig. 3 shows the relative 'spacing of the marking impulses, the carrier input impulses for each voice channel, the voice 'and carrier modulated radio impulses transmitted by the ararngement of Fig. l, and the signal or voice impulses transmitted to the various voice channels in the arrangement of Fig. 2;

Fig. 4 shows a modulator circuit suitable for use in the transmitting arrangement of Fig. 1;

Fig. 5 shows an amplifier-detector circuit suitable for use in the receiving arrangement of Fig. 2;

Fig. 6 'shows', a reiving arrangement alternative to that of Fig, 2; and

Fig. 7 shows the relative spacing of the marker, carrier, signal and switching impulses in a system comprising Figs. 1 and 6.

The telephone oiiice shown in Fig. 1 comprises a radio transmitter 100 common to a plurality of groups of voice channels and associated individual modulators, two groups being shown. One group consists of voice channels C1 1 1, C112, C1 1-3 and C114 and modulators M111, M112, M113 and M114; and a second group consists of voice channels C121,l C122,l C123 and` C124 and modulators M121, `M122, 12,3,A and M124. Each of the modulators maybe sir'r'iilar to that shown in Fig. 4. While each df the gifoups is shown to consist of four channels each, the groups` may consist of a larger numbrof channels. Two sources of alternating curreiit'are shown, thesource 105 being a source of cairier current impulses for the modulators and thesource 103 lb'eing a source of marking impulses each of marks the beginning of a train of signal impulses, one from each modulator in succession. Thev marking impulse source 103 generatescurrentoi one frequency, for instance, 100,'0o1) 'cycles per second and the carrier .current source 105 generates current of some other frequeriiiyio instance, 300,000 cycles per second, suitable `for niigulation by voice current. Timing 'means 104 controls both sources 103 and 105 to transmit impulses in synchronism at a desired rate, fr instance, 10,000 impulsesper second. The marking impulses are applied directlyr through conductors 101 and 1021 tothe input terminals of the radio transmitter 100. The carrier :current impulsesar'e applied to the modulators of each group a train of similar delay lriet- Works N1, N2, N3 and N4 Aconnected in series, there fbeing as many off these networks as there are modulators in a group. A dilerent modulator of each Vgroup is connected in parallel to the output side of teach network and each of the networks delays each carrier current impulse for a like desired intervalof time; so that the modulators in each group are successively rendered effective to transmit a voice 'modulated carrier current impulse the radio transmitter. T'hus the application of each carrier current impulse from source 105 to modulators M111 and M121 is delayed by network N1 lfor the desired interval iollowing the transmission of the corresponding marking ii'npulse from source103 to radio transmitter 100; the application of each carrier current impulse to modulators M1 '121 and M122 is delayed by networks N1 and N2 in series; the applivcation of each carrier` @current vimpulse to modulators M113 and M123 is delayed by networks N1, N2 and N3 in series-Land the application of each carrier 4current impulse to -modulators M1 li and M124 is delayed by networks N1, N2, N3 and N4 in series. Thus, the application of each marking impulse to the radio transmitter 100 is followed in succession by a voice modulated carrier current impulse Vfromeach of modulators M11 1, M112, M113 and M114 in the iirst group. A group delay iilter connects the output of each of the modulators M121, M122, M123 and M124 vin vthe Second group to the radio transmitter and eachof the voice modulated .carrier current impulses from each of these modulators is thereby delayed for an interval equal to the total delay of a carrier impulse by all of networks N1, N2, N3 and N4. Thus, the successive application of the voice modulated carrier current impulses from the modulators of the second group to the radio transmitter 100 follows Athe application of the voice modulated impulses from the modulators of the first group. If there are other groups of modulators, a group delay filter similar to GN1 will be provided for each such other group to delay the application of the voice modulated carrier impulses 'from the modulators of each group in succession.

Referring to Fig. 3 the line 300 represents the spaced application of marker impulses to the radio transmitter and the simultaneous transmission oi Vcarrier current impulses to the first delay network N1; the lines 301 to 304 represent the application of the corresponding carrier current impulses to the modulators of both groups; and the line 305 represents the spaced transmission of the voice modulated :carrier current impulses from both groups of modulators, each marker impulse M being followed in succession by signal impulses 111, 112, 113, 114, 121, 122, 123 and 124 from the correspondingly numbered modulators.

The telephone olice shown in Fig. 2 comprises a radio receiver 200 common to a plurality of amplier-detector units and associated voice channels for selectively receiving signal impulses from the modulators and voice channels of Fig. 1. The receiver output is transmitted through conductors 201 and 202 to the input terminals of each of the normally non-responsive amplier: detectors D211, D212, D213, D214, D221, D222, D223 and D224 associated individually with voice channels C211, C212, C213, C214, C221, C222, C223 and C224, respectively. Each of the amplifier-detectors may be similar to that shown in detail in Fig. 5. The radio receiver 200 is also connected to iilter 203 which is tuned to pass the marker impulses from source 103 without passing the impulses successively transmitted from the modulators of Fig. 1. Thus each incoming marker impulse is applied through lter 203 and delay networks N211, N212, N213, N214, N221, N222, N223 and N224 in succession to the amplifier-detectors in succession. Each of these delay networks delays the marker impulses for an interval equal to the delay of the carrier current impulses in the delay networks of Fig. l. Thus each marker impulse is applied through network N211 to render the amplier-detector D211 responsive to the signal impulses from modulator M211; through networks N211 and N212 in series to render the amplier-detector D212 responsive to the signal impulses from modulator M212; through networks N211, N212 and N213 in series to render the amplifier-detector D213 responsive to the signal impulses from modulator M213; through networks N211, N212, N213 and N214 in series to render the amplifier-detector D214 responsive to the signal impulses from modulator M214; through networks N211, N212, N213, N214 and N221 in series torender the amplifier-detector D221 responsive to the signal impulses from modulator M221; through networks N211, N212, N213, N214, N221 and N222 in series to render the amplier-detector D222 responsive to the signal impulses from modulator M222; through networks N211, N212, N213, N214, N221, N222 and N223 in series to render the amplifierdetector D223 responsive to the signal impulses from modulator M22 3; and through networks N2 I 1, N212, N213, N214, N221, N222, N223 and N224 in series to render the amplifier-detector D224 responsive to the signal impulses from modulator M224. Thus the incoming signal impulses 111, i12, 13, 114, 212, 222, 223 and 224 represented in line 305 of Fig. 3 are selectively transmitted in succession through amplifier-detectors D211, D2i2, D213, D214, D221, D222, D223 and D224, respectively, as indicated in lines 311 to 318 of Fig. 3.

rIhe modulator shown in Fig. 4 comprises a voice current input transformer 40|, a carrier current input transformer 402, vacuum tube amplifier 403 and an output transformer 404. The

amplifier-detector shown in Fig. 5 comprises a signal input transformer '501, a marker impulse input transformer 502 and rectifier 503, resistor 604, vacuum tube amplifier 510, coupling transformer 515, detector tube 520 and voice output transformer 521. The amplifier 510 is normally biased to the cut-off point. Each marker impulse -is applied through transformer 502 and rectifier lment similar to that shown in Fig. 1 comprises a radio receiver 600 and two groups of amplifierdetector units and associated voice channels. The first group includes the amplifier-detectors Dl i, D612, D613 and D614 individually associated with voice channels C611, C612, C613 and C654; and the second group includes the ampli- `ner-detectors D621, D622, D623 and D624 individually associated with voice channels C621,

C622, C623 and C624. The output of radio receiver 606 is directly connected by conductors 601 and 662 to the input side of each of the amplifierdetectors of the second group and is connected through a group delay network GN61 to the amplifier-detectors of the first group. The output of radio receiver 600 is also connected to the selector of marker impulses 603 whichl in response to each incoming marker impulse causes the gen- `eration of a switching impulse by source 604.r The switching impulses thus generated are transmitted through delay networks N61, N62, N63 and N64 in succession. The switching impulses are thus applied to amplifier-detectors D61 1 and D621 at the same time; then to amplifier-detectors D612 and D622 at the same time; then to amplifier-detectors D613 and D623 at the same time; and last to amplifier-detectors D614 and D624 at the same time. Due to the delay vintroduced by group delay network GNBI, the signal impulses from modulator M111 are applied t0 amplifierdetector D611 at the same time that the signal impulses from modulator M121 are applied to amplifier-detector D621; and at this time a switching impulse from network N61 renders these amgender-detectors effective to pass signal energy into the associated voice channels C611 and C621. The signal impulses from modulator M112 are applied to amplifier-detector D612 at the same time that the signal impulses from modulator M622 are applied to amplifier-detector D622; and at this same time a switching impulse from nettive to pass lsignal energy into the associated voice channels C612 and C622. The signa1 impulses from modulator M113 are applied to amplifierdetector D623 at the same time that .signal impulses from modulator M623 are applied'to amplifler-detector D623; and at this same time a switching impulse from network N63 renders these amplifier-detectors effective to pass signal energy into the associated voice channels C613 and C623. Finally, the signal impulses from modulator M114 are applied to amplifier-detector D614 at the same timethat the signal impulses from modulator M124 are applied to amplifierdetector D624; and at this same time a switching impulse from network N64 renders these amplifier-detectors effective to pass signal energy into the associated voice channels C614 and C624.

The relation ofthe marker, carrier, signal and switching impulses in a system comprising Figs. 1 and 6 isshown in lines 101 through 112 of Fig. 7. The legends adjacent these lines render them self-explanatory.

What is claimed is:

l. In a time division multiplex telephone system, a plurality of voice frequency channels, a modulator for each of said channels, a transmission medium, means connecting each of said modulators to said medium, a carrier current source, means for successively applying impulses of carrier current from said source to each of said modulators in succession thereby to effect the cyclic transmission of a voice modulated car.

rier impulse from each of said modulators in suc.. cession to said transmission medium.

2. In a time division multiplex telephone system, a plurality of voice frequency channels, a modulator for each of said channels, a transmission medium, means connecting each of said modulators to said medium, a carrier current source, means comprising timing Ameans and delay networks for vsuccessively applying impulses of carrier current from said source to each of said modulators in succession thereby to effect the cyclic transmission of a voice modulated carrier impulse from each of said modulators in succession to said transmission medium.

3. In a time division multiplex telephone system, a .plurality of voice frequency channels, a modulator for eachof said channels, a transmission medium, means connecting each of said modulators to said medium, a source of marker impulses connected to said medium, means for generating carrier current impulses synchronized with said marker impulses, and means for transmitting each carrier current impulse to said modulators in succession thereby to effect the' cyclic transmission to said medium of a marker impulse followed by a voice modulated impulse'from each of said modulators in succession.

4. In a time division multiplex telephone system, a plurality of voice frequency channels, aV

modulator for each of said channels, a transmission medium, 'means connecting each of said modulators to said medium, a source of marker impulses connected to said medium, meansl for generating carrier current impulses synchronized with said marker impulses, and means comprising delay networks, one for each of said modulators, for transmitting each of said carrier current impulse to said modulators in succession thereby to effect the cyclic transmission to said medium of a marker impulse followed by a voice modulated impulse from each of said modulators in succession. l I

-a -plilralltyoi signal impulses .of yvoice .modulated 'carrier'currenu said supersonic frequency being :different 'from .the frequency of said carrier cur- ;rent,:a plurality of voice,frequency-channels, a ld'etector Sfor each voice channel, an amplifier `connectingeach 'detector to vsaid transmission `medium, means .normal-ly vbiasing each of said A'ampliiiers to Vprevent `thetransmission ofsignal :impulses "to the associated detector, :means com- -prisi'ng fdelay `networks .connected in .series one :foreach offsaid amplifiers for transmitting each vmarker ,impulse to said arnpliiers in succession, A:andmeans in each ampliiier'responsive to each marker limpulse for .rendering the ampliiiereffective to amplify the signal impulse carried by @said transmission medium Whilethe Amarker imi. ,pulse is being applied to the amplifier.

A6. In -combination lin a .time division multipleX telephone system, a plurality of voice channels, a modulator for each channel, said modue `lators divided into aplurality of groups, a source 1 of-carrier currentimpulses, said impulses following each other in timed succession, means com- .prising Ydelay networks connecting said source to said modulators, the output conductors cf each :network being connected to a plurality of modulaters, one in each group land Veach modulator in a group to a diierent network, a transmission ,medium common to said modulators, and means including delay means connecting the modulators of said groups tosaid medium to cyclically transi .mit trains of Voice modulated carrier impulses thereover, each train `consisting of an impulse fromeach of said modulators in succession.

7. In a time division multiplex telephone trans- .mission system, a plurality of voice channels, a

.plurality of modulators, one for each of said voice channels, said modulators divided into groups, a transmission medium common to said modulators, the modulators of one group being directly .connected 'to said transmission medium, delay means including a delay network individual to each of the other groups ofmodulators connect- .ing said other groups of modulators tosaid transmission medium,l a source of carrier current impulses, said impulses following each other in 50 timed succession, means comprising delay-networks equal fin number to the number of modula- -tors in a group 'connecting the carrier current impulse source to said modulators so as to apply each carrier current impulse to said modulators, .one modulator of each group at a time, means directly connecting the modulators of one group rto -saidf transmission medium, and means including delay networks, one for each of the other groups of modulators connecting said. other groups of modulators to said'transmission medium whereby a voice modulated carrier; current impulse is applied to said transmission medium from each offsaid modulators in succession.

. 8. In a time: division multiplex telephone transmission system,-a plurality of voice channels, a plurality of modulators, one for each of said voice channels,-said modulators divided' into groups, a .transmission medium 'commonl to :said modulators, a source of timing impulsesconnected to said g transmission medium, a source of carrier cur-rent and -means for A,generating impulses of carrier -current insynchronism with said timing impulses, means comprising delay networks lequal in number to the number of modulators in a t `group connecting the carrier current impulse `generator to said modulators so as to apply each .carrier current .impulse .to said modulators, one -modulator of each of said groups at a time, means directlyconnectingthe modulators of one of said lgroups to said transmissionlmedium, and means .including delay networks, one for each of the tother of rsaid groupsof modulators, connecting .said other groups of modulators to said trans- .missio'n `medium .whereby a voice modulated carriercurrentimpulse is applied 'to said transmission medium from each of said modulators in succession following each timing impulse applied thereto.

9. -Ina time division multiplex telephone sys- ;tem, a transmission medium carrying marker im- :pulses of alternating current of a supersonic fre- .quency, each marker impulse being followed by -aplurality of signal impulses of voice modulated -carrier current, said supersonic frequency Ibeing dierent 'from the frequency of said carrier current,.a.plurality of voice frequency channels, a `detector for each voice channel, an amplier conznecting each detector to said transmission medium, means normally biasing each of said am- .pliersto prevent the'transmission of signal im- '.,pillsesto the; associated detector, means responisive only to marker imp-ulses for generating corresponding switching impulses, means comprisin'gdelaynetworks connected in seres,one for eachof said amplifiers, for transmitting each switching impulse to said ampliers in succession,.and meansin each amplifier responsive to each switching impulse for rendering the ampli- `fier effective to amplify the signal impulse carriedby said transmission medium while the Yswitching yimpulse is being applied to the amplifier,

.10. YIn a time division multiplex telephone system, ,a plurality of voice channels, a transmission medium carrying marker impulses each followed by a plurality of voice modulated carrier cur- .'rent impulses :in succession, one for each voice channel, ariirst group yof.arnplilier-detectors, a second. group'of ampliiier-.deteotors, each of said ampliiier-detectors individually associated with a .-dierentoneof said voice channels, means di- -rectly connecting the.amplifier-detectors of said 'first group to said transmission medium, means including .a :group delay network 'connecting the Iamplifier-dote' ctors`of said second group to said transmission medium, means responsive to -marker impulses 'received from said transmis- -sion :medium for generating corresponding `zswitching impulses, vmeans comprising other `delay networki forfapplying reach switching impulse to the yamplifierdetectors of said first group in .successione-nd at the same `time applying each -switching;impulseto the amplifier-detectors of -said secondfgroup in' succession whereby the sig- .fnal'energy -of each voice modulated carrier cur- -rent impulse'is transmitted toa different one of said-voicechannels. Y

Y GEORGE W. GILMAN.

,REFERENCES 'CITED .The 'following references are of record in the I-l-le othis patent:

UNrrE-n STATES PATENTS Number 2399,634 yKOch .Q -lm.; May 7, 1940 

